Motor brush holder



Aug. 21, 1962 E. J. THOMASKO MOTOR BRUSH HOLDER Filed Aug. 18, 1958 Fig 1 J M L Z Z fig. 4

3,050,649 Patented Aug. 21, 1962 3,050,649 MOTOR BRUSH HOLDER Elmer J. Thomasko, Elyria, Ohio, assignor to Amherst Metal Products, Incorporated, Amherst, Ohio, a corporation of Ohio Filed Aug. 18, 1958, Ser. No. 755,484 3 Claims. (Cl. 310-247) This invention relates to brush holders of the type used to hold brushes which ride against slip rings, commutators, and the like, and to the process of making those holders from elongated strips of material.

In the past various attempts have been made to form tubular shaped brush holders from flat strips of material by forming the flat strip into a tubular shape. It has been found that when material, which was hard enough to stand the wear from rubbing of the brush was used, that material had a certain amount of spring back or resiliency which tended to open the holder and make its internal dimensions greater than the desired internal dimensions. To overcome this the abutting edges of the strip were staked, soldered, or Welded together after the strip was formed into the tubular shape. The soldering or Welding operation necessarily added costs as well as the problem of holding the edges together and in place during solder- One of the objects of the present invention is to overcome the aforementioned problems and others.

In attaining the objects of the present invention I have developed a new and novel process of constructing a tubular shaped brush holder which has predetermined internal dimensions and which will maintain those dimensions during the installation of the holder in an electric motor or other apparatus.

A further object of the present invention is to provide a brush holder formed from a fiat piece of material and provided with interlocking tabs which overcome any dimension destroying resilient forces inherent in the piece. To this end the interlocking tabs, preferably dovetail shape, are brought into edge to edge engagement and in a uniform partially cylindrical surface, whereby in bringing them together, the metal is so worked as to take advantage of the arch and a resulting increase in interlocking anchoring strength.

Other objects and a fuller understanding of the invention will become apparent from the claims and the following description of a preferred embodiment of the invention illustrated in the attached drawing in which;

FIGURE 1 is a top view of a brush holder and brush assembly incorporating the features of the present invention,

FIGURE 2 is a front view of the brush holder of FIG- URE 1;

FIGURE 3 is an end view of the brush holder of FIG URE 1, and

FIGURES 4, 5, and 6 progressively illustrate the process of iorm-ing the brush holder of FIGURES 1 and 2.

The brush assembly illustrated in FIGURE 1 includes a brush holder 10 which holds a brush 11 having a pig tail 12. The brush H is urged longitudinally or axially of holder 1-0 by a spring =13 compressed between the brush '11 and a cross plate 14 engaging the opposite walls of holder 10. Normally such brushes are in the nature of solid rectangular bars of suitable material.

The brush holder 10 is of tubular shape, in this instance approximately square, and has opposing walls 21 and 22 and opposing walls 23 and 24-, all of which are of the same thickness. The holder 10 has accurate internal dimensions, for example the distance between walls 21 and 22 or between walls 23 and 24, which were predetermined in accordance with the dimensions needed to properly hold rectangular or spare brush 11. The holder 10 also has an axial length extending between end 25 and 26.

It will be noted that tor a considerable portion of their width the Walls 211 and 22 are partially cylindrical, as appears in FIGS. 3 and 6, while adjacent the corners these walls are parallel and at right angles to the walls 23 and 24. This arch has two advantages. First, it forms a shape better suited to guide the brush and permit its free movement, and, second, and more import-ant, it lends itself to a more effective interlocking of tabs at adjoining edges, as will now be described.

As illustrated, there is provided in wall 2 1 a plurality of tabs 30 which interlock with a plurality of tabs 31. Each of these tabs is defined by interconnected edge portions formed by cutting the piece from which the holder is formed on a cut-ting path in such manner that each edge portion of each tab is at an acute angle to its adjacent edge portions. It is understood that even though each edge portion is illustrated as being straight, it may also be slightly curved or include curved portions.

The tubular shaped holder is constructed from an elongated strip of brass or other suitable material which is sufliciently hard to withstand the abrasiveness and wear of sliding movement of the brush thereon. Material of this type has inherent properties which give the piece resiliency and which tend to cause the piece to spring back towards a flat piece after it has been formed into the tubular shaped holder. If the tube were allowed to spring back, the predetermined internal dimensions would be destroyed. The interlocking of the tabs 30 and 31 in wall 21 overcome the dimension destroying resilient properties inherent in the piece and ensure correct internal dimensro-ns.

The process of constructing the tubular shaped holder 10 will now be described. The first step in the process of forming a tubular brush holder 10 of a predetermined length and internal dimensions for holding a square, short rod type of brush 11 in position against a commutator, slip ring or the like, is that of providing an elongated strip 40 having opposite side edges 41 and 42 a width equal to the predetermined axial length of the holder and also having tabs 31 on one end thereof. The next step in the process is that of cutting along a path 43 from one edge 41 to the other edge 42 of the strip 4% to sever a piece 10 from the strip. The piece has been given the same reference numeral as the holder since it will ul-timately be formed into the holder 10. The path 43 includes a plurality of interconnected path portions, such for example path portions 44, 45, 46, 47 and 48 so dispose-d relative to each other that each path portion is at an acute angle to its next adjacent path portion and so that the piece 10 is provided with the tabs 30 and 31 on the respective opposite ends thereof. As illustrated, path portion 46 is at an acute angle to path portions 45 and 47. This makes each tab wider at a distance from the main body part of the piece than it is at the piece so that the tabs on one end of the piece will interlock with the tabs on the newly formed other end of the piece. It is understood that the path portions may be straight and meet at sharp corners, or that they may be slightly curved and meet in rounded corners. Following the cutting, the piece 10- is folded around a mandrel 50, as illustrated in FIGURE 5. The mandrel 50 has dimensions equal to the predetermined internal dimensions desired. This folding forms piece 10 into a generally U-shaped member with the tabs 30 and 31 positioned at the free ends of the legs of the U-shaped member. The next step is that or" bending the legs of said U-shaped member to fold the free ends thereof inwardly towards each other with the tabs 30 and 31 meshing in interlocking engagement with each other. The final step is that of pressing the tabs and the piece against one of the convex surfaces of the mandrel 50 to O lock the tabs 30 and 31 together and to provide the tubular holder with the desired predetermined internal dimensions and to cause the interlocked tabs to overcome any dimension destroying resilient forces inherent in the piece.

It has been found that in bringing the complementary dovetail tabs 30 and 31 together, and in the common longitudinally extending convex surface at each side of which are the corner engaging aligned portions of the wall, the metal is caused to engage with greater precision and certainty, and the pressing of the tabs together results in more eifeotive interlocking than as though these tabs were merely pressed against a fiat surface of a mandrel. The convex portions of both walls 21 and 2 2 obviously lend themselves to stiffening of the finished tubular holder.

The present process of manufacturing a tubular shaped holder as herein described has thus overcome the problems heretofore encountered and provides a tubular shaped holder which meets the objects of the present in vention. Such a holder is of accurate predetermined dimensions. The process of making the tubular holder and the holder produced by the process is new, novel, and less costly than those known heretofore.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of the construction and the combination and arrangement of parts may be resorted to without departing from the object and the scope of the invention as hereinafter claimed.

What is claimed is:

1. A brush holder for electric motors adapted to slidably, tightly embrace a rectangular brush bar and formed of a flat blank of rigid metal and having two parallel fiat sides and an intervening side integral at the corners with the flat sides and formed with a convex, longitudinally extending mid-portion, the opposite longitudinal side of the holder being formed with plane surfaces extending inwardly from the corners at the margins and an intervening, longitudinally extending, convex mid-portion, the

metal of the latter side having complementary, interlocking, dovetailed connection closing the side in the zone of the convex portion and in uniform alignment in said convex zone, said holder thus being shaped to have two of its sides engage the rectangular brush bar only at longitudinally extending narrow marginal surfaces extending inwardly from the corners thereof.

2. The brush holder defined in claim 1 which includes in combination a transverse bridging means at one end of the holder and a compression spring adapted to act against said bridging means and against one end of the brush.

3. A motor brush holder adapted to slidably closely embrace a rectangular brush bar, said holder comprising an integral single piece of metal formed to present opposite sides complementary to two sides of the brush bar having its other two sides formed with inwardly extending margins in the same plane and presenting flat zones extending longitudinally and engaging the brush bar for only a relatively short distance inwardly from its edges, and each of the said latter sides being formed with a convex zone extending longitudinally between said fiat portions adjacent to corners of the holder, one of said sides having a permanently closed seam formed of dovetailed tabs permanently interlocked within and along the convex zone.

References Cited in the file of this patent UNITED STATES PATENTS 206,031 Mather et al. July 16, 1878 728,222 Geisenhoner May 19, 1903 819,866 Dobson May 8, 1906 1,428,195 Wahl et a1 Sept. 5, 1922 1,807,843 Hendrickson June 2, 1931 1,850,679 Leis Mar. 22, 1932 1,999,818 McIntyre Apr. 30, 1935 2,330,207 England et a1. Sept. 28, 1943 2,362,817 Haycock Nov. 14, 1944 2,727,165 Schatfer Dec. 13, 1955 2,763,801 McDonald Sept. 18, 1956 

